The disclosures herein relate generally to heat sinks used in a computer chassis and more particularly to a heat sink having variably spaced fins providing a pressure gradient to enhance natural convection cooling.
The many electrical components in a computer chassis create excessive heat which must be removed to keep the system functioning. Many heat removal schemes are used in this environment including fans, heat sinks and combinations thereof. Heat sinks are often mounted in an abutting relationship with a thermal plate, such as that provided on a microprocessor module, which conducts heat from the module to the heat sink.
In U.S. Pat. No. 5,406,451 a computer system utilizes a heat sink which optimizes the benefits of both linear airflow and turbulent airflow within the computer housing. The heat sink has rows of metal fingers extending from a metal sheet. A fan generates linear airflow within the housing. The heat sink is attached to a heat producing element such that the rows of fingers are placed parallel to the direction of airflow in the housing. The fingers are spaced apart within a single row to generate turbulence in the airflow, and the rows are spaced apart to prevent the turbulence of one row from interfering with the turbulence of an adjacent row.
In U.S. Pat. No. 5,452,181 an apparatus for cooling an integrated circuit device has a fan detachably mounted to a heat sink, and the heat sink is in turn mounted to an exposed surface of the integrated circuit. The heat sink includes a pair of mounting posts, and the fan assembly includes corresponding mounting recesses for receiving the mounting posts. The mounting recesses are dimensioned to form an interference fit with the corresponding mounting posts, in order to retain the mounting posts within the mounting recesses. Alternatively, the fan assembly has biased tabs, which are received within corresponding recesses formed on the integrated circuit device to detachably mount the fan to the heat sink and integrated circuit. An electrical connector with biased terminals is mounted on the fan, and the biased terminals engage corresponding terminals on the integrated circuit upon mounting the fan to the heat sink.
In U.S. Pat. No. 5,504,652, a unitary heat sink is formed of aluminum and includes a planar contact portion for contacting the top of an IC. A number of leg portions extend from the contact portion such that each leg portion has a distal end. The leg portions, being made of the same material as the contact portion, are configured to have a sufficient resiliency such that deformations of the leg portions provide a spring force in the range of 5 to 16 lbs. against the top of the IC.
In U.S. Pat. No. 5,584,339, a heat sink assembly for the central processor of a computer is provided in which the heat sink is selected from metal materials for good thermal conductivity. The heat sink comprises an array of heat conductive posts which define a free space for a fan. A number of grooves disposed between the posts are provided to engage a base plate. The fan is coupled to the base plate and can rotate in the free space. Two columns or rows of the heat conductive posts take the form of a hook such that the base plate when compressed can be engaged with these hooks. The base plate is provided with protrusions to secure to the grooves.
A present trend in the electronics industry is to provide systems not only to be thermally compatible, but more importantly to comply with acoustic requirements, i.e. noise. In addition, cost, component space and reliability requirements prohibit the use of auxiliary fans to be implemented in low-end, cost effective systems. Recent thermal arrangements pose a challenge to provide innovative solutions to thermal management of high power processors in the system.
Without an auxiliary fan in the system, and with the microprocessor residing adjacent a rear end of the chassis, there is a very low air velocity measured at the heat sink/processor interface. A great deal of simulation and experimentation has been performed to attempt to enhance the venting patterns on the power supply and the system chassis. The installation of an auxiliary fan is not always an acceptable solution because it increases the unit cost, noise, and introduces an added reliability concern.
Therefore, what is needed is a heat sink cooling device which does not rely on a fan supplement to enhance air flow across the heat sink and is capable of a self-generated increase in the flow of cooling air across the heat sink to enhance natural convection.